1. Field of the invention
The present invention relates to a developing apparatus provided with a circulation apparatus for circulating a processing solution contained in a tank of the developing apparatus by drive of a pump.
2. Related Art
Generally with a developing processing solution a temperature and degree of exhaustion thereof has an effect on a contrast of finish of a photosensitive material. Therefore, so as to keep the same conditions in processing a plurality of photosensitive materials, it is necesarry to continually maintain a check on the temperature and frequency of use etc. of the developing processing solution. Also, the processing solution inside a developing tank is discharged from a vicinity of a surface of the developing tank solution, and a circulation apparatus is provided for pumping the discharged solution to a bottom portion of the developing tank. The processing solution is thus circulated continually or at regular intervals, and as a result all the processing solution in the developing tank is used uniformly, and nonuniformity of deterioration and temperature is prevented. Further, to keep the action of the developing procesing solution constant, replenishment solution is supplied as an additive to the developing processing solution for each process. The replenishment solution is pumped into the developing tank depending on an operation of a pump for supplying the replenishment solution. An amount of replenishment solution to be supplied is determined depending on a processing amount of photosensitive material. However even if the processing solution is the same, there are cases where there is a difference in the contrast of the finish of the photosensitive material produced by the processing solution at the time or changing all the processing solution in the developing tank with new solution, and the contrast of the finish produced at the time of replenishment of the replenishment solution corresponding to the amount of use. As a result a uniform processing condition cannot be maintained. As shown by a full line in FIG. 3, in the processing of the photosensitive material under a same condition of a processing speed, the contrast is low immediately after the change of the processing solution. Then after replenishment with a predetermined amount of replenishment solution a contrast stabilizing characteristic can be observed.
To avoid this contrast change, it is also possible to have a processing operation in which the processing conveying speed is slowed down at the time of initial change of the processing solution, or a dummy photosensitive material is conveyed, until the contrast of the photosensitive material stabilizes. However, either of the operations is not desirable since with these operations the operability would be impaired. Accordingly, immediately after changing to the new solution, quality impairment must be tolerated for a while.